摘要: Publisher Summary This chapter discusses machine models and simulations. The existence of many different does not necessarily mean that there are no uniform underlying notions computational complexity. In the theory computation, a large variety formal calculi has been proposed to capture notion effective computation. lead proliferation computation theories, because basic fact formalisms have all shown be equivalent in following sense—each one formalism can simulated by other formalism. From equivalence, it concluded if problem is unsolvable particular model, then also for formalized computing devices which this model related mutual simulation. Consequently solvability really depend on used. themselves remain shelf, used when needed.